If you dont believe you can you will never try. If you believe you can there is no reason for anything but relentless work towards your goal. Here i am doing sit up med ball throws with 6lbs. This works core connection as well as reaction. In javelin it doesnt matter how good your technique is if it isnt connected and have good timing. Drills like these are a great chance to lock in those skills. if you dont have a screen to throw at try these with a partner!